This work proposes a high-bandwidth white-light system consisting of a blue gallium nitride (GaN) micro-LED (μLED) exciting yellow-emitting CsPbBr1.8I1.2 perovskite quantum dots (YQDs) for high-speed real-time visible light communication (VLC). The packaged 80 μm × 80 μm blue-emitting μLED has a modulation bandwidth of ∼160 MHz and a peak emission wavelength of ∼445 nm. The achievable bandwidth of the white-light system is up to 85 MHz in the absence of filters and equalization technology. Meanwhile, the bandwidth of the YQDs as a color converter is as high as 73 MHz with the blue GaN μLED as the pump source. A maximum data rate of 300 Mbps can be achieved by taking advantage of the high bandwidth of the white-light system using the non-return-to-zero on–off keying (NRZ-OOK) modulation scheme. The resultant bit-error rate is 2.0 × 10–3, well beneath the forward error correction criterion of 3.8 × 10–3 required for error-free data transmission. In addition, the YQDs which we proposed as a color converter p...

High-Bandwidth White-Light System Combining a Micro-LED with Perovskite Quantum Dots for Visible Light Communication.

Phosphor-converted white light-emitting diodes (pc-WLEDs) are energy efficient and environmentally friendly light sources with a long lifetime, applicable in both display backlights and general lighting. Adding red-emitting phosphors improves the color quality of white LEDs compared to the prototype combination of a blue LED and the yellow Y3Al5O12:Ce3+. Efficient narrow-band red-emitting phosphors like K2SiF6:Mn4+ can meet the market’s needs. This review recapitulates research since 2008 on K2SiF6:Mn4+ as the first and most discussed fluoride phosphor. The limited nephelauxetic effect, typical for fluorides, allows for the tuning of the Mn4+ emission in the red part of the spectrum below 650 nm. This is reflected in the spectroscopic parameters of the crystal field theory. Synthesis methods are described, showing the evolution from etching Si wafers to solution synthesis resulting in consistent luminescent and thermal properties. Though important for applications, long-term stability is often neglected, although (in)organic coatings improving stability emerge. This leads not only to warm-white LEDs with high efficacies and good color rendering, but also to efficient displays with a large color gamut.

K_2SiF_6:Mn^4+ as a red phosphor for displays and warm-white LEDs: a review of properties and perspectives

While perovskite solar cells have skyrocketed in recent years to power conversion efficiencies competitive with those of silicon and thin-film photovoltaics, the lagging behind stability stands in the way of commercialisation. In this review, we discuss the reasons and factors that induce the degradation in photovoltaic performance of perovskite solar cells, and furthermore, we summarise the most promising strategies to enhance the lifespan. We show that each component of the device, including the charge selective contacts, perovskite layer, and electrodes, can be engineered to reduce the influence of heat, UV light, oxygen, moisture and their synergetic effect on the operating lifetime of devices. We conclude that inorganic contacts and inorganic perovskite compositions are the most promising direction toward stable perovskite solar cells.

Enhancement in lifespan of halide perovskite solar cells

Fluorescent semiconductor nanocrystals (quantum dots) have the potential to revolutionize biological imaging, but their use has been limited by difficulties in obtaining nanocrystals that are biocompatible. To address this problem, we encapsulated individual nanocrystals in phospholipid block–copolymer micelles and demonstrated both in vitro and in vivo imaging. When conjugated to DNA, the nanocrystal-micelles acted as in vitro fluorescent probes to hybridize to specific complementary sequences. Moreover, when injected into Xenopus embryos, the nanocrystal-micelles were stable, nontoxic (<5 × 109 nanocrystals per cell), cell autonomous, and slow to photobleach. Nanocrystal fluorescence could be followed to the tadpole stage, allowing lineage-tracing experiments in embryogenesis.

/pdf/in-vivo-imaging-with-quantum-dots-encapsulated-in-3x3r4ful3m.pdf

In vivo imaging with quantum dots encapsulated in phospholipid micelles

Component regulation and crystallization mechanism of CsPbBr3/Cs4PbBr6 perovskite composite quantum dots-embedded borosilicate glass for light emitting application

The spectral optimization for maximizing limited luminous efficacy (LLE) of correlated color temperature (CCT) tunable white light-emitting diodes (LEDs) with two, three and four color perovskite quantum dots (QDs) excited by a blue chip was investigated under the constraint of designated ultrahigh color rendering index (CRI) and color quality scale (CQS). The results show that high quality white lights with CRIs of 96-97, CQSs of 95-96, and LLEs of 243-225 lm/W at CCTs of 2700 K to 6500 K could be realized by the QDs-converted white LEDs (QD-WLEDs) using a blue chip and different combinations of perovskite quantum dots. The luminous efficacies of QD-WLEDs are expected to reach 114 to 122 lm/W at CCTs of 2700 K to 6500 K, if the radiant efficiency of a blue chip is 60% and the real PLQY values of perovskite QDs are 75%. These results demonstrate that perovskite QD-based LEDs are expected to be promising in next generation display and lighting technologies.

Spectral optimization of color temperature tunable white LEDs based on perovskite quantum dots for ultrahigh color rendition

A facile route for highly efficient color-tunable Cu-Ga-Se/ZnSe quantum dots

In this work, transition metal ion- doped zinc-based quantum dots (QDs) are synthesized via a greener controllable method to avoid the toxicity of the traditional cadmium-based QDs and broaden the tunable emission. Herein, the tunable emission of Cu-doped ZnInS/ZnS core-shell QDs (Cu:ZnInS/ZnS) can cover from 500 to 620 nm by varying the Cu dopant concentration from 1 to 20% and the maximum quantum yield can reach 49.8%. Based on the single-doped QDs, Cu,Mn co-doped ZnInS/ZnS core-shell QDs (Cu,Mn:ZnInS/ZnS) with a photoluminance (PL) quantum yield of 30.4% are obtained. All the as-synthesized QDs have the zinc blende structure and the average size is about 3.55 nm. Besides, the interaction mechanism between the Cu and Mn dopant luminescence centers is proposed in this work, which is rarely investigated in the previous report. Diffusion priority and energy transfer between these two dopants are supposed to play an important role in the co-doped QDs and Cu ions could affect the splitting of Mn d states. Color coordinates of these doped QDs show the line-tunability from (0.200, 0.397) to (0.408, 0.508) on the Commission Internationale de L'Eclairage (CIE) chromatic diagram, showing a promising potential in high-quality white light output by integration of these QDs with blue chips.

Wu Yang

Papers

Spectral optimization of color temperature tunable white LEDs based on perovskite quantum dots for ultrahigh color rendition

A facile route for highly efficient color-tunable Cu-Ga-Se/ZnSe quantum dots

Tunable emission of Cu (Mn)-doped ZnInS quantum dots via dopant interaction

Color-tunable optical properties of cadmium-free transition metal ions doped InP/ZnS quantum dots

Controllable synthesis of dual emissive Ag:InP/ZnS quantum dots with high fluorescence quantum yield